feat(sp25): extend TailResource to include acks + ta1_acks

The Acks page needs the same live-tail triplet (useTailStream +
useMergedTail + TailStatusPill) that Claims/Remittances/Activity
already use. The first step is widening the TailResource union so
streamTail("acks") and streamTail("ta1_acks") are valid and the
URL falls out as /api/acks/stream and /api/ta1-acks/stream.

Two new tests assert the URL targets the new backend endpoints.

src/lib/tail-stream.ts

@@ -26,7 +26,7 @@ export type TailEvent =
   | { type: "item_dropped"; data: { id: string } }
   | { type: "error"; data: { message: string } };
 
-export type TailResource = "claims" | "remittances" | "activity";
+export type TailResource = "claims" | "remittances" | "activity" | "acks" | "ta1_acks";
 
 export interface StreamTailOptions {
   /** Forwarded to `fetch`; aborting the controller cleanly exits the generator. */